NASA space materials research

The effect of the space environment on: (1) thermal control coatings and thin polymer films; (2) radiation stability of 250 F and 350 F cured graphite/epoxy composites; and (3) the thermal mechanical stability of graphite/epoxy, graphite/glass composites are considered. Degradation in mechanical properties due to combined radiation and thermal cycling is highlighted. Damage mechanisms are presented and chemistry modifications to improve stability are suggested. The dimensional instabilities in graphite/epoxy composites associated with microcracking during thermal cycling is examined as well as the thermal strain hysteresis found in metal-matrix composites

Prediction of moisture and temperature changes in composites during atmospheric exposure

The effects of variations in diffusion coefficients, surface properties of the composite, panel tilt, ground reflection, and geographical location on the moisture concentration profiles and average moisture content of composite laminates were studied analytically. A heat balance which included heat input due to direct and sky diffuse solar radiation, ground reflection, and heat loss due to reradiation and convection was used to determine the temperature of composites during atmospheric exposure. The equilibrium moisture content was assumed proportional to the relative humidity of the air in the boundary layer of the composite. Condensation on the surface was neglected. Histograms of composite temperatures were determined and compared with those for the ambient environment

Construction and measurements of a vacuum-swing-adsorption radon-mitigation system

Long-lived alpha and beta emitters in the $^{222}$Rn decay chain on (and near) detector surfaces may be the limiting background in many experiments attempting to detect dark matter or neutrinoless double-beta decay, and in screening detectors. In order to reduce backgrounds from radon-daughter plate-out onto the wires of the BetaCage during its assembly, an ultra-low-radon cleanroom is being commissioned at Syracuse University using a vacuum-swing-adsorption radon-mitigation system. The radon filter shows ~20$\times$ reduction at its output, from 7.47$\pm$0.56 to 0.37$\pm$0.12 Bq/m$^3$, and the cleanroom radon activity meets project requirements, with a lowest achieved value consistent with that of the filter, and levels consistently < 2 Bq/m$^3$.Comment: 5 pages, 3 figures, Proceedings of Low Radioactivity Techniques (LRT) 2013, Gran Sasso, Italy, April 10-12, 201

SOME LEGAL PROBLEMS CONNECTED WITH STOCK MARKET TRANSACTIONS

If any one were asked what was the most dramatic event of the last year, he probably refer at once to the collapse of the great Bull Market on the New York Stock Exchange. This was not only a dramatic event, but it was literally a tragedy for hundreds of thousands of people. Securities shrank to less than half their former inflated values and hundreds of millions of dollars in cash and paper profits were lost over night, or possibly we should say over two nights, for the crash occurred in two stages, one in October and one in November, and many of those who staggered through the first were annihilated by the second. Never before had so many people been involved in stock market speculation, and, consequently, never before had so many people been directly hit by any stock market panic. Never before had so many dreams of El Dorado been shattered

Structures and materials technology issues for reusable launch vehicles

Projected space missions for both civil and defense needs require significant improvements in structures and materials technology for reusable launch vehicles: reductions in structural weight compared to the Space Shuttle Orbiter of up to 25% or more, a possible factor of 5 or more increase in mission life, increases in maximum use temperature of the external surface, reusable containment of cryogenic hydrogen and oxygen, significant reductions in operational costs, and possibly less lead time between technology readiness and initial operational capability. In addition, there is increasing interest in hypersonic airbreathing propulsion for launch and transmospheric vehicles, and such systems require regeneratively cooled structure. The technology issues are addressed, giving brief assessments of the state-of-the-art and proposed activities to meet the technology requirements in a timely manner

Characterising a Si(Li) detector element for the SIXA X-ray spectrometer

The detection efficiency and response function of a Si(Li) detector element for the SIXA spectrometer have been determined in the 500 eV to 5 keV energy range using synchrotron radiation emitted at a bending magnet of the electron storage ring BESSY, which is a primary radiation standard. The agreement between the measured spectrum and the model calculation is better than 2%. PACS: 95.55.Ka; 07.85.Nc; 29.40.Wk; 85.30.De Keywords: Si(Li) detectors, X-ray spectrometers, detector calibration, X-ray response, spectral lineshapeComment: 11 pages, 11 PostScript figures, uses elsart.sty, submitted to Nucl. Instrum. Meth.

Alloy oxidation as a route to chemically active nanocomposites of gold atoms in a reducible oxide matrix

While nanoparticles are being pursued actively for a number of applications, dispersed atomic species have been explored far less in functional materials architectures, primarily because composites comprising dispersed atoms are challenging to synthesize and difficult to stabilize against sintering or coarsening. Here we show that room temperature oxidation of Au–Sn alloys produces nanostructures whose surface is terminated by a reducible amorphous oxide that contains atomically dispersed Au. Analysis of the oxidation process shows that the dispersal of Au in the oxide can be explained by predominant oxygen anion diffusion and kinetically limitedmetalmass transport, which restrict phase separation due to a preferential oxidation of Sn. Nanostructures prepared by oxidation of nanoscale Au–Sn alloys with intermediate Au content (30–50%) show high activity in a CO-oxidation probe reaction due to a cooperative mechanism involving Au atoms as sites for CO adsorption and reaction to CO2 embedded in a reducible oxide that serves as a renewable oxygen reservoir. Our results demonstrate a reliable approach toward nanocomposites involving oxide-embedded, atomically dispersed noble metal species

Alloy oxidation as a route to chemically active nanocomposites of gold atoms in a reducible oxide matrix

While nanoparticles are being pursued actively for a number of applications, dispersed atomic species have been explored far less in functional materials architectures, primarily because composites comprising dispersed atoms are challenging to synthesize and difficult to stabilize against sintering or coarsening. Here we show that room temperature oxidation of Au–Sn alloys produces nanostructures whose surface is terminated by a reducible amorphous oxide that contains atomically dispersed Au. Analysis of the oxidation process shows that the dispersal of Au in the oxide can be explained by predominant oxygen anion diffusion and kinetically limitedmetalmass transport, which restrict phase separation due to a preferential oxidation of Sn. Nanostructures prepared by oxidation of nanoscale Au–Sn alloys with intermediate Au content (30–50%) show high activity in a CO-oxidation probe reaction due to a cooperative mechanism involving Au atoms as sites for CO adsorption and reaction to CO2 embedded in a reducible oxide that serves as a renewable oxygen reservoir. Our results demonstrate a reliable approach toward nanocomposites involving oxide-embedded, atomically dispersed noble metal species

Advanced materials for space

The principal thrust of the LSST program is to develop the materials technology required for confident design of large space systems such as antennas and platforms. Areas of research in the FY-79 program include evaluation of polysulfones, measurement of the coefficient of thermal expansion of low expansion composite laminates, thermal cycling effects, and cable technology. The development of new long thermal control coatings and adhesives for use in space is discussed. The determination of radiation damage mechanisms of resin matrix composites and the formulation of new polymer matrices that are inherently more stable in the space environment are examined